Only Iran knows how many mines it has placed in the Strait of Hormuz. But even the possibility that it has littered the narrow waterway with the deadly weapons is forcing the US to begin preparing to scour the seabed for them.
It could take weeks to complete such a painstaking mission and for the route to be declared safe from mines, which may be camouflaged to look like rocks and can burrow into the sands, according to experts.
It would be even longer if the fragile ceasefire between Tehran and Washington collapses and the mission has to be attempted under fire. US president Donald Trump said on Tuesday that he was extending the pause in fighting.
“It is a nightmare scenario,” said Kevin Eyer, a former director of training at the US Naval Mine and Anti-Submarine Warfare Command. He estimates it could take a month and a half to carve a safe transit route into the Gulf and up to four months to completely clear the strait, which carries about a fifth of global seaborne oil and gas trade.
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Bryan Clark, a former Pentagon official at the Hudson Institute, suggested that it might be possible to clear a secure passageway within a week, based on a recently conducted war game at the think tank. But completely clearing mines from the Strait of Hormuz might take up to four weeks, he added.
US forces announced earlier this month they were starting a clearance mission. Trump said on Thursday that he had ordered the US Navy to “shoot and kill” any Iranian vessels that were engaged in minelaying.
Iranian parliament speaker Mohammad Bagher Ghalibaf said in televised remarks last Sunday that Iran had “firmly confronted the US mine-clearance attempts”, which it considered a violation of the ceasefire. He added that Iran had even advanced to “the point of confrontation, but the enemy backed down”.
Much will depend on how many mines Iran was able to lay during its eight-week battle with the US and Israel.
US officials say Iran has laid some mines, but the number may be small. The Islamic Revolutionary Guard Corps (IRGC) has said that vessels should avoid sailing through a restricted area in the middle of the strait and use alternative shipping routes passing through Iranian waters so as to avoid mines, according to Tasnim, the semi-official Iranian news outlet affiliated to the guards.
Iran’s declaration this month that the strait would be “completely open” during the period of the Israel-Lebanon ceasefire prompted a rush of ships to attempt to exit the Gulf expecting to be allowed through on a specific route marked out by Iran. Instead, several were fired on by the IRGC including an Indian tanker and a container ship belonging to the French shipping line CMA CGM, prompting confusion over whether the strait was open or not while Trump kept a US naval blockade in force. The majority that had decided to attempt the crossing turned around.
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It is the uncertainty that is the main problem. “If they have dropped a single mine, then you have to assume that they have dropped more,” said Eyer. For a safe corridor to be opened through the strait, demining vessels would need to clear a roughly mile-wide channel whose co-ordinates could be shared with tankers to allow them to be shepherded through.
Iran is believed to have had a pre-war stockpile of between 5,000 to 6,000 mines. They range from antiquated contact mines, which are tethered and float just below the surface, to sophisticated bottom-lying mines which are programmed to explode in response to specific magnetic, acoustic and pressurise signatures.
“This will be tedious and tough work,” said Steve Wills, a former officer aboard a US minesweeper who now works with the Center for Maritime Strategy.
Iran probably dumped its mines quickly and haphazardly, making them harder to find compared with more methodically patterned minefields, said Scott Savitz, a senior engineer at RAND who has advised the Pentagon on mine warfare.
Lightly-armed minehunting vessels moving slowly would also be vulnerable to cruise missiles and drones fired from the nearby Iranian coastline, he said. They would need to be shadowed by advanced destroyers and fighters overhead.
The Littoral Combat Ships will bear the brunt of the work. They search for mines by using helicopters equipped with lasers and by dispatching unmanned vehicles, which are armed with sonar, cameras and sensitive magnetic field detectors. The LCS programme has been criticised by some analysts and veterans for being expensive and untested.
But the US Navy only has two such vessels ready to begin work in the strait, while a third is undergoing maintenance in Singapore.
The US has neglected its mine warfare capacities for decades and had been in the process of retiring its last dedicated minesweepers, despite mines being responsible for almost 80 per cent of US warships sunk or disabled since 1945.
Washington withdrew the last four wooden-hulled Avenger-class vessels from Bahrain in January. Two Avengers are being redeployed from Japan towards the Middle East.
“Nobody wants to put money into something as unsexy as mine warfare,” said Eyer.
This limited capacity may explain why Trump has stepped up his campaign to pressure US partners in Europe, which have more than 100 mine-hunting vessels and a wealth of expertise, to contribute to an effort to clear the strait.
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“They need some kind of support from Europe,” said Jan Thörnqvist, a former head of the Swedish Navy. Europeans were more experienced and better equipped than their American counterparts, Thörnqvist said, adding that the currents and coastal waters in the Strait of Hormuz were similar to the Danish straits.
There are discussions in Europe, whose navies have long practised clearing mines in the Baltic and North Sea, about putting together a mission. But many countries are reluctant to help solve a problem which they had no hand in creating.
It would not be a quick fix, either. It could take as long as four months to outfit and deploy a European mine clearance operation, Thörnqvist said, adding that any clearance operation would then take several months.
If the Europeans do not make an appearance in the Gulf, Washington could call on another force to assist its stretched sailors: mine-hunting dolphins.
These specially trained swimmers, based in San Diego, were deployed during previous mine-clearing campaigns in the Gulf in 1991 and in 2003. They could plausibly be used in a clear-up campaign once the bulk of the mines have been identified and destroyed.
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“They are exceptional in their ability to locate objects buried in the seafloor,” said Savitz, who added the dolphins could still best some of the most advanced mine-hunting technologies that the US could muster.
It could be an opportunity to prove their worth. “I have been hearing continually how we are on the verge of acquiring capabilities that will greatly exceed those of the dolphins,” said Savitz. “I am still waiting.”- The Financial Times, additional reporting by Charles Clover and Alice Hancock.
